Tractive apparatus are known for hauling a cable by means of a lever system actuating two self-clamping grippers with a reciprocal movement which drives the two grippers in opposite directions while causing the gripper which moves in the haulage direction to clamp on the cable and the other gripper which moves in the opposite direction to be unclamped. Each of the grippers is formed by two opposite jaws between which the cable may be clamped and which are joined together by clamping links pivotably mounted on these two jaws.
Guiding of the reciprocal movement of the grippers may be provided by a rectilinear bar having an appropriate profile on which is guided a jaw of each gripper and at one end of which is pivotably mounted the operating lever which actuates two links pivotably mounted on this lever at two symmetrical points with respect to the pivoting point between the guide bar and the lever, these two links driving respectively the two grippers.